The invention relates to an optical wavelength multiplexing and/or demultiplexing device. The device has a first light guide and at least three further light guides and a phase grating. The grating is arranged in the radiation path between the first light guide and the further light guides.
Such a device is known, for example, an article by H. W. Yen entitled "Planar Rowland spectrometer for fiber-optic wavelength demultiplexing" (Optics Letters, December 1981, Vol. 6, No. 12, pages 639-641). The phase grating splits the polychromatic light by dispersion in a single diffraction order, generally the first order. In order to obtain a sufficiently large difference between the diffraction angles of the various wavelengths which are situated comparatively close to each other (20 to 40 nm) grating period must be comparatively small. Therefore, the manufacture of such phase gratings is very intricate. As
Only lasers may be used as the light sources in the known device. Light emitting diodes, which emit light in a range of approximately 20 nm around a central wavelength, are not suitable. Because of the strong dispersion of the known demultiplexer, light from a diode would be emitted in such a wide angular range that a substantial part of the light would not reach the light guide (a glass fiber) intended to carry this wavelength.